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Development of Continuous Deflection Device

The selection of optimum rehabilitation strategies for distressed jointed concrete pavements is one of the biggest challenges that transportation agencies face. Hot-mix asphalt (HMA) overlays of concrete pavement are commonly used nationwide as a rehabilitation alternative but are considered a short-term solution because of the presence of reflection cracking. Other frequently used alternatives include joint replacement, dowel bar retrofit, and slab fracturing techniques. Key engineering information needed to develop the selection of optimum rehabilitation strategies includes the load transfer efficiency (LTE) at joints, structural uniformity, and void detection. This information can be obtained with traditional equipment such as falling weight deflectometers (FWD) but obtaining sufficient data with this device is slow, cost prohibitive, and exposes workers and the public to risk. Consequently only a very small percentage of the joints are tested on current rehabilitation projects. Quantifying the number and location of poor joints is critical in developing cost-effective rehabilitation strategies. There exists a need to develop a device that can rapidly provide 100% coverage of existing joint condition in order to support development of long-lasting pavement rehabilitation designs. Several continuous deflection devices have been developed as alternatives to FWDs. While these devices offer the potential of 100% coverage at higher speeds (1 mph) as compared to an FWD, there remain concerns as to the cost and operational feasibility of such a device and the magnitude of the further developmental effort needed to make the devices practical for use on rapid renewal projects. The objective of this project is to critically assess the potential of existing continuous deflection devices as a practical and cost-effective tool for use in the development of optimum pavement rehabilitation strategies on rapid renewal projects. This assessment will examine: (1) The potential demand by and value to public agencies. (2) The technical capabilities (including accuracy and repeatability of test results and ability to provide meaningful data), limitations (field applications, equipment configuration, operating and safety characteristics), and other impediments to implementation of existing devices. (3) Further development of the technology including both hardware and software needed to make these tools practical for use.